When I was a new 2LT, a very old-looking (to me) Army Colonel gave me a handfull of empty cases and told to hang onto them, as they were pretty rare. I did put them away, and found them in a recent move. From what I could gather at the time, this was a very short run of experimental blank cartridges for the M16. All of the rest of them were destroyed in a rotary kiln in 1972. They are all-aluminum 5.56 blank cartridges with a FA 71 headstamp. Frankfort Arsenal was closed down in the eighties. Here are a couple of photos with a standard 5.56 cartridge for comparison. Has anyone seen these before? What are they worth?

This may help . Not sure if its exactly your cartridge but its pretty darn close ...

In 1971 or so Frankford Arsenal was making a blank similar to this , with aluminium body and full length mock bullet "projectile" . This was done to facilitate feeding , particularly during automatic fire in the M16 rifle.

Originally a straight open-mouth bullet style was used. These are found with a bare aluminium case , and a gold anodized exterior also.

A slight taper was added to enhance feeding , and then more taper - as per your examples- was added to more closely approximate a bullets ogive.

This configuration was designated as the XM200E1 Blank. It was being tested by the Test and Evaluation Command pending standardisation but was withdrawn due to problems with the orifice size in the blank firing adaptors on the M16 rifle.

This blank case can be found in many variances , from differant mouth sizes , powder differances, casewall thickness variations , machined "scratches" on the casewall , holes for pressure testing and so on.

Does that help? Hope so . Thanks to the book " History and Development of the M16 Rifle and its Cartridge " by the late David R. Hughes.
P.143-144

If you have a spare I would be a candidate for purchase , please.

Sure I'll sell some. I don't think I have enough years left to wait 40 more years to find them again. What should I ask for them, $20 each?